The purpose of this project is to study the pathogenesis of recurrent aphthous stomatitis with the ultimate aim of preventing this condition by effective treatment and prevention. The recently initiated protocol aims at investigating the pathogenesis of aphthous stomatitis by both clinical and immunological studies. The clinical research involves investigating patients hematologically and from a general medical point of view to determine the incidence of precipitating factors involved in the pathogenesis of aphthous stomatitis. The incidence of food allergies is being explored and in vitro food allergy tests are being carried out in order to assess their specificity and sensitivity. The relationship between gluten-induced (celiac) disease and aphthous stomatitis is also being investigated. In addition, a double-blind trial into the effects of zinc sulfate tablets is being investigated. In vitro laboratory immunological tests are also being carried out in patients and in a control population. These tests involve lymphocyte transformation, assays for lymphokine and monokine and also assays of suppressor cell function. Finally, family studies are being carried out on these patients including HLA studies.